The present invention relates to a powder inhaler for administering powder by inhalation.
A number of powder inhalers are known which use different systems for introducing a dose of powder into an air stream. Typically, the powder is inhaled into the lungs of a patient in order to treat, for example, asthma.
EP-A-0237507 discloses one such powder inhaler. This inhaler comprises an inhalation channel and a mouthpiece which includes an air chamber and an outlet nozzle, which together define a flow path through which a stream of air is drawn during inhalation by a user. This inhaler further comprises a dosing mechanism for providing a dose of powder to the inhalation channel. During inhalation, air is first drawn into and through the inhalation channel so as to pick up powder. The stream of air containing powder is then drawn through the air chamber and out of the outlet nozzle of the mouthpiece.
FIG. 1 illustrates such a powder inhaler. The inhaler comprises an inhaler unit 1 and a cap 2 which is a screw fit to the same. The inhaler unit 1 comprises a mouthpiece 3 which includes an outlet nozzle 4, an inhaler body 6 and a rotatable grip portion 8 for operating a dosing mechanism for providing doses of powder for inhalation. The inhaler body 6 is provided with an opening 10 which is filled with a window 11 through which an indicating wheel 42 is visible so as to provide an indication as to the usage of the inhaler.
FIG. 2 illustrates in exploded view component parts disposed within and to the inhaler body 6. The inhaler body 6 is capped with a divider 12 which is fixed thereto. For aesthetic reasons the inhaler body 6 is an opaque moulding. The divider 12 is a transparent moulding which includes a peripheral groove 13 and an adjacent peripheral ridge 14 by which the mouthpiece 3 is attached thereto. The divider 12 further includes a depending tongue 15, a part of which forms the window 11.
Within the inhaler body 6 are housed the component parts of the dosing mechanism. These component parts include a dosing unit 16 which comprises a member 17 having a planar surface in which a plurality of dosing elements 18 are provided and a s haft 20 which extends axially from the centre of the member 17, a distribution unit 22 which comprises an inhalation channel 24 and a storage unit 26 which comprises a storage chamber 28 for storing powder. The above-mentioned component parts of the dosing mechanism are assembled by passing the inhalation channel 24 through an opening 30 in the storage unit 26 and passing the shaft 20 through central openings 32, 34 in the distribution unit 22 and the storage unit 26 respectively. When so assembled, the upper ends of the inhalation channel 24 and the storage chamber 28 pass respectively through first and second openings 36, 38 in the divider 12. In this way, the distribution unit 22 and the storage unit 26 are fixed in position in relation to one another and the dosing unit 16 can be rotated relative thereto.
In this inhaler the storage chamber 28 is open at the bottom such that in use powder is provided to the dosing unit 16 under the action of gravity and the distribution unit 22 further comprises scrapers 40 which are resiliently biased against the surface of the member 17 of the dosing unit 16 in which the dosing elements 18 are provided. In this way, as the dosing unit 16 is rotated, the dosing elements 18, which in this inhaler comprise a plurality of through holes, are filled with powder by the scrapers 40. Powder is prevented from passing through the dosing elements 18 by a plate (not illustrated) which is disposed beneath the dosing unit 16.
The divider 12 further includes a supporting member 41 for rotatably supporting an indicating wheel 42. The indicating wheel 42 includes a plurality of teeth 44 disposed around the periphery thereof which engage with a spiral groove or protrusion 46 on the end face of the shaft 20 of the dosing unit 16. The supporting member 41 is configured to align the indicating wheel 42 such that a part of the periphery thereof is disposed adjacent the inner surface of the window 11. In use, as the dosing unit 16 is rotated, the spiral groove or protrusion 46 engages with one or more of the teeth 44 on the indicating wheel 42 so as to rotate the same. In this way, by providing a coloured marking on the periphery of the indicating wheel 42, it is possible to provide the user with a visible indication at the window 11 as to the usage of the inhaler.
As illustrated in FIG. 4, the mouthpiece 3 is fixed to the divider 12. The mouthpiece 3 comprises first and second parts 48, 50, the first part 48 being the part which is gripped in the lips of a user and the second part 50 being an insert fitted within the first part 48. The second part 50 comprises a tubular section 52 which includes one or more spirally or helically shaped projections 54 that act to deflect the air drawn therethrough and thereby deagglomerate any larger particles of entrained powder and a substantially radially-directed flange 56 which provides a surface that together with upper surface of the divider 12 defines an air chamber 58 that is in fluid communication with the inhalation channel 24 through which air containing powder is drawn on inhalation by a user. The flange 56 includes a downwardly-depending annular skirt 59 which is a tight fit within the first part 48 and acts to fix the second part 50 to the first part 48.
In use, as described hereinabove, powder is transferred from the storage chamber 28 to one of the dosing elements 18, and, with rotation of the dosing unit 16, the one dosing element 18 provides a dose of powder to the inhalation channel 24. In this inhaler the dosing unit 16 is rotated by rotating the grip portion 8 in the clockwise sense when viewed from below between first and second angularly-spaced positions. For this purpose, the dosing unit 16 includes wedge-shaped elements 60 disposed around the periphery of the member 17 thereof and the grip portion 8 comprises a resilient member (not illustrated) which is configured to engage with an axially-directed surface 60a of a respective one of the wedge-shaped elements 60 so as to rotate the dosing unit 16 by pushing the respective wedge-shaped element 60. On rotation of the grip portion 8 in the opposite, counter-clockwise sense between the second and the first angularly-spaced positions, the dosing unit 16 remains stationary and the resilient member is located behind the axially-directed surface 60a of the adjacent wedge-shaped element 60; the resilient member riding over an inclined surface 60b of the adjacent wedge-shaped element 60.